Semiconductor device

ABSTRACT

In order to block hydrogen ions produced when forming an interlayer insulating film by HDP-CVD or the like to thereby suppress an adverse effect of the hydrogen ions on a device, in a semiconductor device including a contact layer, a metal interconnection and an interlayer insulating film on a semiconductor substrate having a gate electrode formed thereon, the interlayer insulating film is formed on the metal interconnection by bias-applied plasma CVD using source gas containing hydrogen atoms, and a silicon oxynitride film is provided in the underlayer of the metal interconnection and the interlayer insulating film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor devices, and moreparticularly to a semiconductor device having a hydrogen trappingfunction by insertion of a silicon oxynitride film.

2. Description of the Background Art

Multilevel interconnection configuration has increasingly been employedto achieve higher integration and higher performance of devices. Tofabricate a semiconductor device having multilevel interconnections, forexample, a lower-layer aluminum interconnection is formed firstly, and asilicon oxynitride film serving as an interlayer insulating film isformed on the lower-layer aluminum interconnection by CVD (ChemicalVapor Deposition) or SOG (Spin On Glass), and then an upper-layeraluminum interconnection is formed on the silicon oxynitride film.

Such multilevel interconnection configuration leads to an increase incomplexity as well as a higher aspect ratio of the uneven surfaceportion of the element, which may cause a break of wire. Thus, for thepurposes of increasing the yield of the interconnections and improvingreliability, planarization and smoothing are important. Currently, aTEOS (Tetra Ethoxy Silane)/O₃ oxide film, a SOG film or the like hasbeen used for such planarization and smoothing.

The silicon oxide film formed by CVD or SOG, however, contains a largeamount of water (H₂O or OH), which causes degradation in reliability ofthe device, particularly, degradation of hot-carrier resistance of aMOSFET (Metal-Oxide Semiconductor Field-Effect Transistor). To suppresssuch degradation due to the water from the TEOS/O₃ film, it has beenreported that an ECR (Electron Cyclotron Resonance)-SiO₂ film may bedeposited under the TEOS/O₃ film, in which case a great number ofdangling bonds present in the ECR-SiO₂ film can capture water from theTEOS/O₃ oxide film to prevent penetration of the water to the device(see N. Shimoyama et al., “Enhanced Hot-Carrier Degradation due to Waterin TEOS/03 Oxide and a New Method of Water Blocking using ECR-SiO₂Film”, SDM 92-33, pp. 51-56).

Further, there is another way of addressing this problem of water bydepositing an oxide film on a first interconnection by plasma CVD, toblock water desorbing from an insulating film provided in its upperlayer. It has been reported that a SiO₂ film formed by plasma CVD usingSiH and N₂O gases under a low pressure of 1.5 Torr, and a TEOS filmformed by plasma CVD by lowering the flow rate of TEOS/O₃, can blockwater and suppress MOSFET hot-carrier degradation (see Kimiaki Shimokawaet al., “Water Desorption Control of Interlayer Dielectrics to ReduceMOSFET Hot Carrier Degradation”, IEICE TRANS. ELECTRON., VOL. E77-C, NO.3, MARCH 1994, pp. 473-479).

Meanwhile, it is known that a Si-rich and N-rich plasma CVD film canblock water from an interlayer insulating film such as a SOG film. Thisfilm can readily be formed with SiH₄ and N₂O gases by adding N₂ gasunder a low pressure, and has a function of absorbing water andreleasing hydrogen (see Peter Lee et al., “MOISTURE TRAPPING AND PINHOLESUPPRESSION BY THE USE OF HIGH REFRACTIVE INDEX PECVD SIO₂ THIN FILM”,VMIC Conference, Jun. 7-8, 1994, ISMIC-103/94/0299, pp. 299-301).

Further, it has been reported that, in a semiconductor device having aninsulating film formed by CVD using a source gas having Si—H bonds,moisture resistance is improved by setting the amount of the Si—H bondsin the insulating film to 0.6×10²¹ cm⁻³ or less and by setting Nconcentration to 3×10²¹ cm⁻³ or more, and thus, after completion of thesemiconductor device, water is prevented from reaching a metalinterconnection such as aluminum, resulting in improved reliability ofthe semiconductor device. The insulating film is formed on theinterconnection, or is used as a passivation film (see Japanese PatentLaying-Open No. 09-289209).

Still further, a semiconductor device having a Si-rich oxide film, a Sioxide film, a SOG film and an oxide film formed sequentially on alower-layer metal interconnection is known. The Si-rich oxide film,serving as an interlayer insulating film, is formed on the metalinterconnection, or is used as a passivation film. It is reported thatthis semiconductor device ensures hot carrier reliability and goodperformance characteristic of the semiconductor element (see JapanesePatent Laying-Open No. 09-129625).

SUMMARY OF THE INVENTION

A silicon oxide film formed by CVD or SOG contains a great amount ofwater, which causes degradation of reliability of the device. One way tosolve this problem of water is to form a P—SiO film serving as aninterlayer insulating film by plasma CVD using TEOS, SiH₄, O₂, N₂O, Aror the like as source gas. Further, there is another method of forming aP—SiO film by CCP (Capacitively Coupled Plasma) CVD using SiH₄, N₂O orthe like as source gas. With these methods, the water that desorbs fromthe interlayer insulating film formed by CVD or SOG and tries topenetrate into the underlayer can be blocked with the P—SiO film.

With advancement in miniaturization of devices in recent years, however,the above-described CVD or SOG has been replaced with HDP (High DensityPlasma) CVD so as to fill in the gaps between the fine-pitch aluminuminterconnections, having a ratio H/W of the height H of theinterconnection to the distance W between the neighboringinterconnections to be 1.0 or greater, with an insulating film. InHDP-CVD, RF (radio frequency) bias is applied to the substrate side toaggressively attract ions, which can significantly improve thegap-filling performance. This however causes a new problem that, in thefilm-forming process by the HDP-CVD, the hydrogen ions (H⁺) dissociatedfrom SiH₄ come to drift due to the RF bias, penetrate into theunderlayer, to thereby degrade the device. Furthermore, the biasincreases the amount of hydrogen penetrating into the underlayer oxidefilm, so that it is necessary to provide a film having a hydrogentrapping function in the underlayer.

An object of the present invention is to provide a semiconductor devicethat is free from the influence of hydrogen ions, by blocking thehydrogen ions produced when forming an interlayer insulating film byHDP-CVD or the like.

A semiconductor device according to the present invention includes acontact layer, a metal interconnection and an interlayer insulating filmon a semiconductor substrate having a gate electrode formed thereon. Theinterlayer insulating film is formed on the metal interconnection bybias-applied plasma CVD using source gas containing hydrogen atoms. Asilicon oxynitride film is provided in an underlayer of the metalinterconnection and the interlayer insulating film.

Preferably, the silicon oxynitride film is formed immediately under themetal interconnection, or immediately over an etch stopper film of thegate electrode, or in the contact layer. The silicon oxynitride film maybe formed by plasma CVD, using source gas containing either N₂O or O₂,and SiH₄. The silicon oxynitride film having Si of 34 atomic % to 40atomic %, O of 48 atomic % to 60 atomic %, and N of 5 atomic % to 12atomic % may be formed.

Preferably, the silicon oxynitride film is subjected to heat treatmentat a temperature of not lower than 450° C., and has N, B, P or Asintroduced therein. In the silicon oxynitride film, H in Si—H bonds ispreferably not more than 8×10 ²¹ atoms/cm³, and more preferably not morethan 1×10²¹ atoms/cm³, by Fourier transform infrared (FT-IR)spectroscopy. Further, the film where peak of Si—O bonds is at a wavenumber of not less than 1020 cm⁻¹ and not more than 1075 cm⁻¹ by FT-IRspectroscopy and no peak of Si—N bonds (wave number: 835 cm⁻¹) isdetected by FT-IR spectroscopy is suitable.

Preferably, the silicon oxynitride film has tensile stress, and has athickness of not less than 100 nm and not more than 600 nm. Theinterlayer insulating film is formed by high-density plasma CVD. Amultilayer type semiconductor device may be provided by forming aplurality of layers of the metal interconnections and a plurality oflayers of the interlayer insulating films. Further, the presentinvention is applicable generally to semiconductor devices including atunnel insulating film, a control electrode, a floating electrode, and afirst metal interconnection, wherein the first metal interconnection hasa ratio H/W of a height H of the interconnection to a distance W betweenthe neighboring interconnections, and the ratio H/W is not less than1.0.

According to the present invention, the hydrogen ions that dissociatewhen forming the interlayer insulating film on the metal interconnectioncan be trapped to suppress hot-carrier degradation, NBTI (Negative BiasTemperature Instability) degradation and degradation of the tunnelinsulating film attributable to the hydrogen ions. Particularly, it ispossible to prevent degradation of hot-carrier resistance of a MOSFETdevice, variation in threshold value due to degradation of the tunneloxide film in an AND or NOR type flash memory, or an adverse effect ofthe hydrogen ions on a device that requires a low-temperature process ofnot higher than 400° C. such as an MRAM or the like.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are conceptual diagrams showing structures of semiconductordevices of the present invention fabricated in Examples 1-3,respectively.

FIGS. 4A and 4B show data of an untreated silicon oxynitride film and asilicon oxynitride film heat-treated at about 800° C., respectively,obtained by FT-IR (Fourier Transform InfraRed) spectroscopy.

FIG. 5 is a conceptual diagram showing the structure of thesemiconductor device of the present invention fabricated in Example 1.

FIGS. 6A, 6B and 6C are conceptual diagrams showing structures of amemory portion, a selected transistor portion and a peripheral circuit,respectively, of an AND-type flash memory device according to thepresent invention.

FIG. 7A is a conceptual diagram showing the state where a contact holefor an electrode is formed in a silicon oxynitride film and a contactlayer in the case where the silicon oxynitride film is formedimmediately beneath a metal interconnection, and FIG. 7B is a conceptualdiagram showing the state where a contact hole for an electrode isformed in a silicon oxynitride film and a contact layer in the casewhere the silicon oxynitride film is formed in the contact layer.

FIG. 8A is a conceptual diagram showing the state where a siliconoxynitride film is formed immediately beneath a first metalinterconnection and etching is conducted to form a contact via forconnecting the first metal interconnection with a second metalinterconnection, and FIG. 8B is a conceptual diagram showing the statewhere etching is conducted to form a contact via for connecting firstand second metal interconnections, without forming a silicon oxynitridefilm immediately beneath the first metal interconnection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A typical example of the semiconductor device of the present inventionis shown in FIG. 1. As shown in FIG. 1, the semiconductor deviceincludes a contact layer 3, a metal interconnection 4 and an interlayerinsulating film 5 on a semiconductor substrate 2 having a gate electrode1 formed thereon, and is characterized in that it has a siliconoxynitride film 6 in the underlayer of metal interconnection 4 andinterlayer insulating film 5. When interlayer insulating film 5 isformed on metal interconnection 4 by bias-applied plasma CVD using asource gas including hydrogen atoms such as SiH₄ or the like, thehydrogen ions would drift in the film-forming process due to the bias,and would penetrate into the underlayer. In the present invention,however, the silicon oxynitride film having the effect of trapping thehydrogen ions is provided in the underlayer of metal interconnection 4and interlayer insulating film 5, so that it is possible to preventoccurrence of degradation of the device due to the hydrogen ions.Further, even in a multilayer semiconductor device having a plurality ofmetal interconnections and a plurality of interlayer insulating filmsformed therein, the silicon oxynitride film can effectively trap thehydrogen ions, whereby reliability of the device is improved.

With miniaturization of devices, HDP-CVD has been used for filling inthe gaps between the metal interconnections of a finer pitch after the90-nm node. In the film-forming process by HDP-CVD, RF bias is appliedto the substrate side, so that a great amount of hydrogen ionsdissociated from SiH₄ would penetrate into the underlayer. According tothe present invention, however, even when forming an interlayerinsulating film by HDP-CVD, the hydrogen ions can effectively be trappedto prevent their penetration into the gate insulating film. Accordingly,it is possible to suppress hot-carrier degradation, NBTI degradation, aswell as degradation of the tunnel insulating film.

Although the present invention is generally effective for semiconductordevices, it is also particularly effective for a flash memory device ofNOR type, AND type or the like, in which it is necessary to form aninterlayer insulating film by HDP-CVD so as to fill in the gaps betweenthe fine-pitch aluminum interconnections. Further, in a product to whicha low-temperature process of 400° C. or lower is applied as in the caseof a MRAM (Magnetic RAM), a PRAM (Phase Change RAM), or a semiconductordevice incorporating both of them, for example, not only the amount ofhydrogen contained in the interlayer insulating films is increased byHDP-CVD, but also the amount of hydrogen contained in other interlayerfilms increases. The present invention is effective particularly in sucha case.

FIGS. 6A-6C show an example where the present invention is applied to anAND-type flash memory device. FIG. 6A shows a memory portion, FIG. 6Bshows a selected transistor portion, and FIG. 6C shows a peripheralcircuit. As shown in FIG. 6A, the memory portion is configured with atunnel insulating film 61, a control electrode 64 and a floatingelectrode 63, and also has an assist electrode 62 and a siliconoxynitride film 65. As shown in FIG. 6B, the selected transistor portionhas a first metal interconnection 66 made of W and a second metalinterconnection 69 made of Al. Metal interconnections 66 and 69 areconnected via a contact via 60 a. Metal interconnection 66 and aninterconnection in the lower layer are connected via another contact via60 b. Further, an interlayer insulating film 67 a is formed on firstmetal interconnection 66 by bias-applied plasma CVD, using source gascontaining hydrogen gas. A silicon oxynitride film 65 is formedimmediately beneath first metal interconnection 66. The presentinvention is effective even for the semiconductor device where theinterlayer insulating film needs to be formed by HDP-CVD so as to fillin the gaps between the fine-pitch interconnections where the ratio H/Wof the height H of first metal interconnection 66 to the distance Wbetween the neighboring interconnections is 1.0 or greater, as shown inFIG. 6B. FIG. 6C shows, by way of example, a peripheral circuit thatincludes a silicon oxynitride film 65 on a contact layer (TEOS film) 68b, and has an interlayer insulating film (HDP-CVD film) 67 b formed onan interlayer insulating film (p-TEOS film) 68 a.

The silicon oxynitride film is provided in the underlayer of theinterlayer insulating film, so as to trap the hydrogen ions dissociatedfrom the interlayer insulating film that would otherwise penetrate intothe underlayer. The silicon oxynitride film may be formed below theinterlayer insulating film and above the metal interconnection to trapthe hydrogen ions from the interlayer insulating film. With thisconfiguration, however, void will occur in the silicon oxynitride filmwith normal CVD when the interconnection pitch becomes smaller, so thatit is not possible to address the finer-pitch interconnections. Thus, inthe semiconductor device of the present invention, the siliconoxynitride film is formed in the underlayer of the interlayer insulatingfilm and the metal interconnection.

More specifically, as shown in FIG. 1, the silicon oxynitride film 6 isformed immediately beneath metal interconnection 4. Alternatively, asshown in FIG. 2, the silicon oxynitride film 26 is formed immediatelyabove an etch stopper film 27 of a gate electrode 21. Stillalternatively, as shown in FIG. 3, the silicon oxynitride film 36 isformed within contact layers 33 a, 33 b. Although the similar effect oftrapping hydrogen ions can be enjoyed in any of these cases, theconfiguration to form the silicon oxynitride film immediately beneaththe metal interconnection is preferable in that etching when forming acontact hole for an electrode in the contact layer becomes easy.

FIGS. 7A and 7B each show the state after formation of a contact hole 72for an electrode through silicon oxynitride film 75 and contact layer71. FIG. 7A shows the case where silicon oxynitride film 75 has beenformed immediately above the contact layer 71 so as to form siliconoxynitride film 75 immediately beneath the metal interconnection. FIG.7B shows the case where silicon oxynitride film 75 has been formed incontact layer 71. When silicon oxynitride film 75 is formed immediatelyabove contact layer 71, as shown in FIG. 7A, contact hole 72 is formedas follows. Firstly, silicon oxynitride film 75 is etched to create anopening (first step), and next, contact layer 71 formed of an oxide filmsuch as TEOS or the like is etched to create an opening (second step).Since silicon oxynitride film 75 and contact layer 71 differ in etchingrate from each other, they are etched in separate steps as describedabove. Meanwhile, in the case where silicon oxynitride film 75 is formedwithin contact layer 71, as shown in FIG. 7B, it is necessary to formthe contact hole by switching between three steps of: etching of thecontact layer (oxide film such as TEOS or the like), etching of thesilicon oxynitride film, and etching of the contact layer. This willcomplicate the etching process, in which case failure in opening of thecontact hole as shown in FIG. 7B is likely to occur. Thus, it ispreferable to form silicon oxynitride film 75 immediately above contactlayer 71, as shown in FIG. 7A.

FIGS. 8A and 8B each show the state where etching has been conducted toform a contact via for connecting first and second metalinterconnections. With miniaturization of devices, misalignment of thevia 83 with respect to the first metal interconnection 86 becomesinevitable, as shown in FIG. 8B, in which case a slit-like opening 87will be generated at the misaligned portion to extend through theunderlying contact layer 81, which would cause a short circuit whenforming a W plug afterwards. However, when the silicon oxynitride film85 is inserted immediately beneath first interconnection 86, as shown inFIG. 8A, silicon oxynitride film 85 serves as an etch stopper film evenin the event of misalignment of via 83, since the etching rate ofsilicon oxynitride film 85 is slower than those of the other oxidefilms. This can prevent formation of an opening through contact layer81.

One conceivable way of fabricating the device will be to form a contactlayer and an electrode therethrough, then form a SV (Stacked Via) layermade of a TEOS layer and a silicon oxynitride film or the like, bury anelectrode in the SV layer and join it with the electrode in the contactlayer, and then form a metal interconnection thereon. With this method,however, formation of the electrode in the SV layer in alignment withthe electrode in the contact layer is difficult, and the number ofmanufacturing steps increases. Thus, it is preferable to fabricate thedevice by forming a contact layer and a silicon oxynitride film, forminga contact hole and an electrode, and then forming a metalinterconnection thereon. This facilitates fabrication of the device andreduces the production cost as well.

The silicon oxynitride film is made of a composition of SiON. If theamount of Si increases, the percentage of Si in the non-bonded statewithin the silicon oxynitride film increases, which is preferable inthat the hydrogen ion trapping function is enhanced. From thisstandpoint, the silicon oxynitride film of the present inventionpreferably has a composition where Si is from 34 atomic % to 40 atomic%, O is from 48 atomic % to 60 atomic %, and N is from 5 atomic % to 12atomic %. The silicon oxynitride film having such a composition may beformed by plasma CVD, using source gas containing either N₂O or O₂, andSiH₄.

When the silicon oxynitride film is formed by plasma CVD using sourcegas containing SiH₄, Si—H bonds are produced. H in the Si—H bonds ispreferably not more than 8×10²¹ atoms/cm³, more preferably not more than4×10²¹ atoms/cm³, and most preferably not more than 1×10²¹ atoms/cm³, byFT-IR spectroscopy, from the standpoint of enhancement of the hydrogenion trapping function. The hydrogen ion trapping sites for trapping thehydrogen ions may be increased by subjecting the silicon oxynitride filmhaving been formed to heat treatment. This can suppress release of theonce trapped hydrogen ions and can significantly improve the hydrogenion trapping function. The heating temperature is preferably not lowerthan 450° C., more preferably not lower than 600° C., and mostpreferably not lower than 700° C.

The hydrogen ion trapping sites may also be increased by introducingions of N, B, P or As into the silicon oxynitride film, or by providingthe silicon oxynitride film with tensile stress. Furthermore, thehydrogen ion trapping sites may be increased by increasing the densityof dangling bonds, or by X-ray irradiation or UV irradiation. With thesemethods, a silicon oxynitride film where H in the Si—H bonds is not morethan 1×10²¹ atoms/cm³ by FT-IR spectroscopy can be obtained. Further, itis possible to form a silicon oxynitride film in which peak of the Si—Obonds by FT-IR spectroscopy is at the wave number of not less than 1020cm⁻¹ and not more than 1075 cm⁻¹, and peak of the Si—N bonds (wavenumber: 835 cm⁻¹) is not detected. Such a silicon oxynitride film ispreferable in that its hydrogen ion trapping capability is great.

FIGS. 4A and 4B each show data of a silicon oxynitride film by FT-IRspectroscopy. FIG. 4A shows FT-IR data of an untreated film, and FIG. 4Bshows data of the silicon oxynitride film having undergone heattreatment at about 800° C. In the silicon oxynitride film heat-treatedat about 800° C., H in the Si—H bonds is 0.8×10²¹ atoms/cm³ by FT-IRspectroscopy, and peak of the Si—O bonds by FT-IR spectroscopy is at thewaver number of not less than 1020 cm⁻¹ and not more than 1075 cm⁻¹, andpeak of the Si—N bonds (wave number: 835 cm⁻¹) is not detected.

The preferable thickness of the silicon oxynitride film varies dependingon its chemical composition or the like. However, in general, it ispreferably not less than 100 nm and more preferably not less than 250nm, from the standpoint of ensuring sufficient hydrogen ion trappingfunction. Although the trapping function increases as the thickness ofthe silicon oxynitride film increases, too thick a film would suffercracking. Thus, it is preferably not more than 600 nm and morepreferably not more than 350 nm.

EXAMPLE 1

FIGS. 1 and 5 show a structure of a semiconductor device fabricated inthe present example. FIG. 1 shows only the basic elements from among theconstituent elements shown in FIG. 5, for better understanding of thepresent invention as well as for facilitating comparison with thesemiconductor devices shown in FIGS. 2 and 3.

As shown in FIG. 5, firstly, a p-type well 52 a was formed on asemiconductor substrate 52, and a field oxide film 58 was formed on asurface of p-type well 52 a. Next, a gate oxide film 58 c was formed onp-type well 52 a, and a gate electrode 51 was formed on gate oxide film58 c. A sidewall spacer 51 a was formed on the side surface of gateelectrode 51.

A SiN film serving as an etch stopper film 57 was formed on gateelectrode 51 and, using gate electrode 51 and sidewall spacer 51 a asmasks, impurity ions were implanted, to form a source region 58 a and adrain region 58 b on the respective sides of gate electrode 51.Thereafter, a TEOS film was formed as a contact layer 53, and a siliconoxynitride film 56 was formed on contact layer 53.

Silicon oxynitride film 56 was formed by plasma CVD, using SiH₄ (flowrate: 100 cm³/min) and N₂O (flow rate: 1 L/min) as source gas.Thereafter, it was' subjected to heat treatment at 450° C. under the N₂atmosphere. This silicon oxynitride film had a composition of Si of 37atomic %, O of 55 atomic % and N of 9 atomic %, and H in the Si—H bondswas 6×10²¹ atoms/cm³ by FT-IR spectroscopy. The film thickness was 250nm.

Next, a metal interconnection 54 of Al was formed on silicon oxynitridefilm 56, and an interlayer insulating film 55 was formed on metalinterconnection 54. Interlayer insulating film 55 was formed by HDP-CVD,using SiH₄ (flow rate: 100 cm³/min), O₂ (flow rate: 100 cm³/min), and Ar(flow rate: 100 cm³/min) as source gas. HDP-CVD was carried out at 1 kW,by applying RF bias of 13.56 MHz.

When interlayer insulating film 55 is formed by HDP-CVD, the hydrogenions dissociated from SiH₄ during the forming process come to drift dueto the RF bias and penetrate into the underlayer. According to SIMS(Secondary Ion Mass Spectroscopy), the hydrogen ions penetrating intothe underlayer was 1×10²¹ atoms/cm³ or more. In the present example,however, the silicon oxynitride film was formed immediately beneath themetal interconnection, and no hydrogen ion penetrating into theunderlayer was observed.

EXAMPLE 2

In Example 1, silicon oxynitride film 6 was formed immediately beneathmetal interconnection 4, as shown in FIG. 1. In the present example, asilicon oxynitride film 26 was formed immediately above an etch stopperfilm 27 of a gate electrode 21, as shown in FIG. 2. That is, in thepresent example, an etch stopper film 27, a silicon oxynitride film 26,a contact layer 23, a metal interconnection 24, and an interlayerinsulating film 25 were formed on a semiconductor substrate 22 having agate electrode 21 formed thereon. The semiconductor device wasfabricated in the similar manner as in Example 1, except that the orderof forming the layers was different as described above.

In the semiconductor device thus fabricated, the silicon oxynitride filmhad a composition of Si of 38 atomic %, O of 53 atomic %, and N of 10atomic %, H in the Si—H bonds by FT-IR spectroscopy was 5×10²¹atoms/cm³, and the film thickness was 300 nm. In the present example, nohydrogen ion penetrating through the silicon oxynitride film into theunderlayer was observed by SIMS.

EXAMPLE 3

In Example 1, silicon oxynitride film 6 was formed immediately beneathmetal interconnection 4, as shown in FIG. 1. In the present example, asilicon oxynitride film 36 was formed in contact layers 33 a, 33 b, asshown in FIG. 3. That is, in the present example, an etch stopper layer37, a contact layer 33 b, a silicon oxynitride film 36, a contact layer33 a, a metal interconnection 34, and an interlayer insulating film 35were formed on a semiconductor substrate 32 having a gate electrode 31formed thereon. Except for the difference in order of forming thelayers, the semiconductor device was fabricated in the similar manner asin Example 1.

In the semiconductor device thus fabricated, the silicon oxynitride filmhad a composition of Si of 36 atomic %, O of 52 atomic % and N of 10atomic %, H in the Si—H bonds by FT-IR spectroscopy was 7×10²¹atoms/cm³, and its thickness was 280 nm. In the present example, therewas no hydrogen ion observed by SIMS that penetrates through the siliconoxynitride film into the underlayer.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. A semiconductor device including a contact layer, a metalinterconnection and an interlayer insulating film on a semiconductorsubstrate having a gate electrode formed thereon, wherein saidinterlayer insulating film is formed on said metal interconnection bybias-applied plasma CVD using source gas containing hydrogen atoms, anda silicon oxynitride film is provided in an underlayer of said metalinterconnection and said interlayer insulating film.
 2. Thesemiconductor device according to claim 1, wherein said siliconoxynitride film is formed immediately under said metal interconnection.3. The semiconductor device according to claim 1, wherein said siliconoxynitride film is formed immediately over an etch stopper film of saidgate electrode.
 4. The semiconductor device according to claim 1,wherein said silicon oxynitride film is formed in said contact layer. 5.The semiconductor device according to claim 1, wherein said siliconoxynitride film is formed by plasma CVD.
 6. The semiconductor deviceaccording to claim 5, wherein said silicon oxynitride film is formedusing source gas containing either N₂O or O₂, and SiH₄.
 7. Thesemiconductor device according to claim 6, wherein said siliconoxynitride film has Si of 34 atomic % to 40 atomic %, O of 48 atomic %to 60 atomic %, and N of 5 atomic % to 12 atomic %.
 8. The semiconductordevice according to claim 1, wherein said silicon oxynitride film issubjected to heat treatment at a temperature of not lower than 450° C.9. The semiconductor device according to claim 1, wherein said siliconoxynitride film has H in Si—H bonds of not more than 8×10²¹ atoms/cm³ byFourier transform infrared (FT-IR) spectroscopy.
 10. The semiconductordevice according to claim 1, wherein said silicon oxynitride film has N,B, P or As introduced therein.
 11. The semiconductor device according toclaim 1, wherein in said silicon oxynitride film, H in Si—H bonds is notmore than 1×10²¹ atoms/cm³ by FT-IR spectroscopy, peak of Si—O bonds isat a wave number of not less than 1020 cm⁻¹ and not more than 1075 cm⁻¹by FT-IR spectroscopy, and no peak of Si—N bonds (wave number: 835 cm⁻¹)is detected by FT-IR spectroscopy.
 12. The semiconductor deviceaccording to claim 11, wherein said silicon oxynitride film has tensilestress.
 13. The semiconductor device according to claim 1, wherein saidsilicon oxynitride film has a thickness of not less than 100 nm and notmore than 600 nmn.
 14. The semiconductor device according to claim 1,wherein said interlayer insulating film is formed by high-density plasmaCVD.
 15. The semiconductor device according to claim 1, wherein aplurality of layers of said metal interconnections and a plurality oflayers of said interlayer insulating films are formed.
 16. Thesemiconductor device according to claim 1, including a tunnel insulatingfilm, a control electrode, a floating electrode, and a first metalinterconnection, wherein the first metal interconnection has a ratio H/Wof a height H of the interconnection to a distance W between theneighboring interconnections, and the ratio H/W is not less than 1.0.